The present invention relates to a method for electrochemical machining. More particularly, this invention relates to a method for enabling a work blank disposed opposite an electrode across a gap to be machined to desired shape and dimensions by causing the action of electrochemical dissolution to be concentrated upon or confined to the points of the work blank required to be removed.
By a mechanical method of machining, it is difficult to machine a material or work blank such as of heat-resisting alloy to a complicated shape without deformation. For this reason, the electrochemical method has come to find an increasingly popular acceptance in this sort of machining.
According to the conventional electrochemical machining method, a given work blank and a cathode are disposed very close to each other (across a gap of from 0.02 to 0.7 mm) in an electrolyte and a flow of direct current having a high current density of 30 to 300 A/cm.sup.2 is passed between the work blank and the cathode. In this case, the equilibrium gap (the gap between the cathode and the work blank) must be decreased in order to increase the machining speed and enhance the machining accuracy. This inevitably requires the current density to be maintained at a sufficiently high level by constantly feeding the cathode toward the work blank as the machining work progresses. This is because a decrease in the current density lowers the metal removal effect (amount of metal removed/amount of electricity passed), making it no longer possible to continue the machining operation.
When the electrochemical machining is performed by using a direct current in an electrolyte kept at rest, the ions, gases, etc. which are formed by the electrochemical reaction involved stagnate between the two electrodes and consequently interfere with maintenance of high current density and also bring about a local buildup of heat in the electrolyte, preventing the machining operation from being continued smoothly. To avoid this trouble, therefore, it has been necessary for the electrolyte to be forcibly circulated at a high rate of not less than 10 m/sec. thoughout the entire period of machining operation. In order for the electrolyte to be kept in circulating motion at such a high rate of speed, however, there is required incorporation of a flow generating device. If, in this case, the electrodes are in the form of fine wires, the moving electrolyte produces a force which vibrates the electrodes and degrades the machining accuracy. It is further sometimes the case that the work blank has a shape such as to impede effective flow of the electrolyte, making it no longer possible to perform the desired machining on the work blank at all.
An object of the present invention is to provide a method for electrochemical machining which enables a given work blank to be machined highly efficiently without requiring the electrolyte to be forcibly circulated.